Table 2:

Diagnosis code-only algorithms performance

Primary		Predicted	True	Sens	PPV	Spec	Kappa
	Algorithm: Synchronous
Lung	Overall	6,445	6,789	0.74	0.78	0.98	0.73 (0.72 – 0.74)
	Adenocarcinoma	2,643	2,806	0.75	0.79	0.97	0.74 (0.72 – 0.75)
	Carcinoma	539	571	0.75	0.79	0.97	0.74 (0.70 – 0.77)
	NSCLC	664	745	0.73	0.82	0.97	0.74 (0.71 – 0.77)
	Other	723	784	0.74	0.80	0.99	0.75 (0.73 – 0.78)
	SCLC	1,079	1,144	0.74	0.78	0.97	0.72 (0.69 – 0.74)
	Squamous	797	739	0.72	0.67	0.98	0.68 (0.65 – 0.71)
Breast	Overall	294	203	0.60	0.41	1.00	0.49 (0.43 – 0.54)
	Her2−/Hr+	167	86	0.57	0.29	1.00	0.39 (0.31 – 0.46)
	Her2+/ Hr(+/−)	34	31	0.55	0.50	1.00	0.52 (0.37 – 0.67)
	Other	55	50	0.60	0.55	1.00	0.57 (0.46 – 0.68)
	Triple (−)	38	36	0.69	0.66	1.00	0.67 (0.55 – 0.80)
Skin	Overall	197	230	0.72	0.84	1.00	0.78 (0.73 – 0.82)
	MMJN	*	*	0.43	0.60	1.00	0.50 (0.15 – 0.85)
	Nevi & Melanomas	177	206	0.72	0.84	1.00	0.77 (0.73 – 0.82)
	Other	15	17	0.82	0.93	1.00	0.87 (0.75 – 1.00)
	Algorithm: Lifetime
Lung	Overall	12,126	6,789	0.85	0.48	0.89	0.55 (0.54 – 0.56)
	Adenocarcinoma	4,807	2,806	0.86	0.50	0.88	0.56 (0.55 – 0.58)
	Carcinoma	780	571	0.83	0.61	0.92	0.65 (0.62 – 0.68)
	NSCLC	1,102	745	0.84	0.57	0.89	0.61 (0.58 – 0.64)
	Other	1,359	784	0.84	0.49	0.93	0.58 (0.55 – 0.60)
	SCLC	2,411	1,144	0.86	0.41	0.79	0.45 (0.42 – 0.47)
	Squamous	1,667	739	0.85	0.38	0.93	0.49 (0.46 – 0.51)
Breast	Overall	1,467	203	0.76	0.11	0.98	0.18 (0.16 – 0.21)
	Her2−/Hr+	701	86	0.74	0.09	0.98	0.16 (0.12 – 0.19)
	Her2+/ Hr(+/−)	255	31	0.81	0.10	0.96	0.17 (0.11 – 0.22)
	Other	217	50	0.72	0.17	0.99	0.27 (0.20 – 0.34)
	Triple (−)	294	36	0.83	0.10	0.95	0.17 (0.12 – 0.23)
Skin	Overall	892	230	0.87	0.22	0.97	0.35 (0.31 – 0.38)
	MMJN	150	*	0.86	0.04	0.98	0.07 (0.02 – 0.13)
	Nevi & Melanomas	689	206	0.87	0.26	0.96	0.39 (0.35 – 0.43)
	Other	53	*	0.88	0.28	0.93	0.40 (0.26 – 0.55)

For Medicare claims data algorithms identifying synchronous and lifetime brain metastases based only on the presence of a diagnosis code for secondary cancer of the CNS, this table shows classification accuracy compared to a SEER SBM gold standard. The rows under “Algorithm: Synchronous” represent such an algorithm with the additional criteria that codes must have occurred within 60 days of primary cancer diagnosis, whereas “Algorithm: Lifetime” indicates that codes may have occurred at any time in Medicare claims. “Sens” refers to sensitivity; “spec”, specificity; PPV, positive predictive value. An asterisk (“*”) represents values that are suppressed to avoid reporting data from 1 through 11 cases. NSCLC stands for non-small-cell lung cancer; SCLC, small-cell lung cancer; MMJN, malignant melanoma in junctional nevi.